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Endocrine System Flash Cards.

Course Overview

Class: Anatomy and Physiology II

Date: January 14, 2025

Topics for the Week:

  • Hormone Activity (Tuesday): Understanding the various functions and types of hormones within the endocrine system, including the specific roles of different glands.

  • Hormone Chemistry and Introduction to Glands (Thursday): A deeper dive into the chemical structure of hormones and an overview of major endocrine glands and their functions.

  • Lab Assignment Ex. 1: Due on Sunday, focusing on practical applications and experiments related to hormone activity in the human body.

Quizzes:

  1. Survey Quiz: Initial assessment focusing on student understanding and engagement.

  2. Glands Quiz: Evaluating knowledge of different endocrine glands and their functions.

  3. Ex. 1 Lab Quiz (one attempt only): Testing understanding of lab procedures and findings.

Endocrine System Function

Role:

  • The endocrine system plays a crucial role in maintaining homeostasis, similar to the nervous system, but utilizes hormones (chemical messengers) transported through the bloodstream instead of relying on electrical impulses.

Regulation:

  • Hormones govern metabolic processes, influencing both the formation and breakdown of substances in the body.

  • Example: Growth hormone significantly assists in physical growth and development during childhood and adolescence.

Speed and Duration:

  • The endocrine response is generally slower than the nervous system's, taking minutes to hours to initiate; however, endocrine effects can persist in the body for days or even weeks.

Endocrine Glands

Characteristics:

  • Endocrine glands are ductless, highly vascularized, and secrete hormones directly into the bloodstream, which can present a higher risk during surgical interventions, such as thyroid surgery, due to potential bleeding.

Important Endocrine Glands:

  1. Pituitary Gland: Located below the hypothalamus; often referred to as the 'master gland' due to its role in regulating various hormonal functions.

  2. Thyroid Gland: Shaped like a butterfly and situated in the throat; produces hormones that regulate metabolism, energy levels, and overall growth.

  3. Parathyroid Glands: Small glands located within the thyroid; responsible for regulating calcium levels in the body.

  4. Thymus: Positioned near the heart; plays a vital role in immune function, particularly during early life by producing T-cells.

  5. Adrenal Glands: Positioned atop the kidneys; produce stress hormones such as cortisol and adrenaline, which help in responding to stress.

  6. Pancreas: Serves a dual role in both the endocrine and digestive systems, secreting insulin and glucagon to regulate blood sugar levels.

  7. Gonads: Include ovaries (female) and testes (male), responsible for the production of sex hormones essential for reproductive functions.

Hormones

Definition:

  • Hormones are defined as chemical messengers that travel through the bloodstream to various target organs, where they exert specific effects on physiological processes.

Functions:

  • Hormones can change cell permeability, influence DNA transcription, affect enzyme activity, and regulate the secretion of other hormones.

  • Example: The growth hormone released from the pituitary gland significantly affects growth in bones and organs, playing a pivotal role in development.

Hormone Mechanisms of Action

Receptor Requirement:

  • Each hormone requires specific receptors to exert its effects; without binding to its receptor, it cannot function biologically.

Types of Hormones:

  1. Steroid Hormones: Cholesterol-based and non-polar; these hormones typically lead to direct gene activation in target cells.

  2. Amino Acid-Based Hormones: Polar hormones that utilize second-messenger systems to trigger cellular responses.

Hormone Characteristics:

  • Half-Life: The duration it takes for a hormone's concentration in the bloodstream to decrease by half.

  • Onset: Time taken from hormone release to the manifestation of its effects in the body.

  • Duration: The overall length of time a hormone remains active within the body before it is metabolized or excreted.

Regulation of Hormone Activity:

  • Up Regulation: An increase in the number of receptors in response to low hormone levels, enhancing cellular sensitivity to that hormone.

  • Down Regulation: A decrease in receptor number due to high levels of a hormone, diminishing how effectively cells can respond to it.

Hormone Interactions

  • Permissiveness: The action of one hormone is dependent on the presence of another hormone.

  • Synergism: The combined effect of two hormones is greater than the sum of their individual effects (e.g., growth hormone synergizing with sex hormones for physical development).

  • Antagonism: Opposing actions of hormones; for example, calcitonin and parathyroid hormone have opposing effects on calcium metabolism in the body.

Feedback Mechanisms

  • Negative Feedback: Many hormones are regulated through negative feedback loops, helping to maintain physiological balance.

  • Example: Temperature regulation through sweating to lower body heat if elevated.

Factors Stimulating Hormone Release:

  1. Humoral Stimuli: Changes in blood levels of ions or nutrients, such as glucose levels, prompting hormone release.

  2. Neural Stimuli: Input from the nervous system can stimulate hormone secretion.

  3. Hormonal Stimuli: Hormones from one gland can stimulate other glands, known as tropins.

Pituitary Gland Functions

  • Referred to as the master gland, the pituitary regulates various body processes through hormone release.

Sections:

  1. Anterior Pituitary: Produces six key hormones essential for different body functions (e.g., TSH, GH).

    • Growth Hormone (GH): Stimulates growth and regulates metabolic functions.

  2. Posterior Pituitary: Stores and releases hormones such as oxytocin (involved in childbirth and lactation) and antidiuretic hormone (ADH), which regulates water balance.

Key Hormones of the Anterior Pituitary:

  • Thyroid Stimulating Hormone (TSH): Stimulates the thyroid gland to produce thyroid hormones.

  • Adrenocorticotropic Hormone (ACTH): Activates the adrenal cortex to release corticosteroids involved in stress responses.

  • Follicle Stimulating Hormone (FSH) & Luteinizing Hormone (LH): These hormones regulate reproductive processes including ovulation and testosterone production.

  • Prolactin (PRL): Initiates and maintains milk production in breast tissue.

Thyroid Gland Functions

  • Thyroid Hormone (TH): Influences metabolic activity throughout the body, playing a critical role in energy metabolism and growth.

  • Hyposecretion can lead to conditions such as cretinism in children, characterized by developmental delays and physical growth deficiencies.

  • Hypersecretion can lead to symptoms associated with hyperthyroidism, including increased metabolism and weight loss.

Parathyroid and Calcitonin

  • Parathyroid Hormone (PTH): Raises blood calcium levels by promoting calcium release from bones and increasing absorption in the intestines and kidneys.

  • Calcitonin: Lowers blood calcium levels by promoting bone formation and reducing calcium release from bones.

Adrenal Glands

  • Medulla: Produces catecholamines such as epinephrine and norepinephrine, which are crucial in the body’s fight-or-flight responses.

  • Cortex: Produces corticosteroids involved in various functions including the body’s response to stress, metabolic regulation, and inflammation control.

Pancreas Functions

  • Insulin and Glucagon: These hormones tightly regulate blood glucose levels; insulin lowers blood sugar levels while glucagon raises them.

  • Diabetes Mellitus: A condition characterized by high blood sugar levels due to inadequate insulin production or action.

Miscellaneous Hormone Producers

  • Pineal Gland: Contributes to circadian rhythms by secreting the hormone melatonin, which regulates sleep-wake cycles.

  • Gonads: Produce sex hormones including testosterone (male), estrogen, and progesterone (female), which influence sexual development and reproductive functions.

  • Thymus: Involved in T-lymphocyte production, essential for immune response.

  • Novel Hormones: Organs such as the heart, kidneys, skin, and placenta also produce hormones that are significant to their specific functions.